1. Field of the Invention
Apparatuses consistent with the present invention relate to a wideband transmission line conversion technique of connecting a coplanar waveguide (CPW) to a parallel transmission line having a predetermined angle from a substrate.
2. Description of the Related Art
Many techniques for connecting a microstrip to another microstrip have been proposed in the related art. FIG. 1 shows the conventional case of connecting a microstrip to another microstrip. Hereinafter, a signal line and a ground line will be collectively referred to as a transmission line for simplicity of description. The signal line 100 and the ground line 102 of two microstrips formed in a mutually orthogonal manner are connected to each other. When two microstrips are connected as shown in FIG. 1, a signal delivered from the signal line 100 of one microstrip is delivered to the signal line 100 of the other microstrip without any reflection. However, a portion of a substrate of one microstrip must be removed in order to connect the substrate disposed in a horizontal direction to the substrate disposed in a vertical direction. That is, the signal lines 100 of the two microstrips can be connected to each other when a portion of one substrate of one microstrip is removed.
In addition, it is assumed that a signal is transmitted from the signal line 100 of the substrate disposed in a horizontal direction to the signal line 100 of the substrate disposed in a vertical direction, and the signal line 100 of the substrate disposed in the vertical direction is disposed from an upward direction toward a downward direction. In this case, a portion of the substrate disposed in the horizontal direction must be removed as shown in FIG. 1, and a transmission line must extend so as to rotate the transmission line 100 of the substrate disposed in the horizontal direction by 180 degrees.
FIG. 2 shows a case of connecting a CPW to a microstrip in the related art. A signal line 200 of the microstrip and a signal line 200 of the CPW, which are disposed in a mutually orthogonal manner, are connected to each other, and a ground line 202 of the microstrip and a ground line 202 of the CPW are connected to each other. However, a connection structure shown in FIG. 2 is disadvantageous in that an area of the ground line is large so that it occupies a large space and a transmission line of the microstrip and a transmission line of the CPW cannot be stably adhered to each other.
As such, a technique of connecting two microstrips to each other and a technique of connecting the CPW to the microstrip have been proposed in the related art. However, a technique of connecting the CPW to the parallel transmission line was not proposed in the related art.